What Causes Severe Migraine With Dizziness?

I've been getting really bad migraine headaches and i am prescribed medicine for it but it still doesn't work. and i get really light headed and dizzy and i have to force my self to eat, and when i am done eating my breast hurt and at night as well. and i always feel like i have to throw up and on Friday i was stressing really bad and that is when i started feeling really sick. my friend told me it's maybe about stress or i might struck a nerve or i might be pregnant.. i don't know whats wrong with me.